Gas metal arc welding (GMAW) is commonly referred to by one subtype, such as metal inert gas (MIG) welding or another subtype, such as metal active gas (MAG) welding, where the shielding gas may be either inert or active, respectively. In these welding processes, an electric arc forms between a consumable wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to melt, and join. Along with the wire electrode, a shielding gas feeds through the welding gun, which shields the process from contaminants in the air. The process can be semi-automatic or automatic. Typically, a constant-voltage, direct current power source is used with GMAW, but constant-current systems, also known as continuous systems, as well as pulsing current systems, can be used.
Another welding subtype is the tungsten inert gas (TIG) welder. In this case, a consumable wire electrode is heated by an ark emitted from tungsten, and the shielding gas is inert. Some TIG and GMAW welders have a pulsing feature built into the welder. The user may access these pulsing settings from the control panel on the front of the welder.
To operate typical continuous welders, the operator applies pressure to an input pedal, which feeds a control signal to the welder. The input pedal provided with a typical continuous TIG or GMAW welder contains a potentiometer and a switch. The potentiometer can be based on a sweeper or a plunger to create the proportional signal. The signal is proportional to the position of the input pedal, producing a pedal position signal, which can vary between 0 and 100%. The welder machine sends inputs a +10 volt or other arbitrary value, such as +5 volts, into the input pedal's potentiometer, and a pedal position signal proportional to the position of the input pedal is sent back out into the machine. For example, when the input pedal is not depressed, a signal equal to zero is returned to the machine. In that case the pedal position signal would be equal to 0 volts, indicating that the input pedal is not pressed. When the input pedal is depressed half way down, a pedal position signal of 5 volts would be returned to the machine, indicating that the input pedal is pressed half-way down. When the input pedal is fully depressed, the full 10 volts would be returned to the machine, indicating that the input pedal is pressed all the way down. These three voltages are just examples, since a continuous range of values between 0 and 10 Volts is possible. Typically, the potentiometer can produce Voltages in steps of approximately 0.1 Volts.
The welder machine also sends +10 volts to a switch inside the input pedal, and this output is sent back to the machine as well. The switch activates and closes the circuit when the input pedal is pressed down approximately 10 percent. When the welder machine detects a minimum of 10 percent of the switch voltage, the torch is activated. Once the torch is activated, it uses the pedal position sensor to indicate how many amps to output to the torch.
In contrast, for a pulsed operation welder, the pedal sends the voltage signal to the welder. This voltage signal is received by circuitry in the welder which converts the input voltage signal into a pulsed signal. The pulsed signal is then used to control the torch. Welders that have pulsing features built into the system are significantly more expensive than welders without pulsing features (i.e., continuous welders). Frequently, that price difference can be up to a factor of two, such that a pulsing welder can cost more than twice as much as a continuous version of the same welder.
Embodiments herein provide a device to retrofit a continuous, constant current, welder to replicate the pulsing functions built in to a pulsing welder. Typically, in order to achieve pulsed welding, it is necessary to purchase a welder with those features already included in the welder, which, as discussed above is significantly more in price.